1. Field of the Invention
The invention relates to combustors for industrial gas turbines, and more particularly modular drop-in combustors that are preassembled in conformity with assembly and function specifications prior to installation into an industrial gas turbine.
2. Description of the Prior Art
Known industrial gas turbines utilize replaceable combustors with flanged connections to access ports in the combustor case. In known combustor designs a generally annular-shaped combustor basket has an open tip portion distal the combustor flange that is inserted in nesting fashion into a corresponding combustor transition along an insertion path that is coaxial with the centerlines of the respective access port, combustor basket and transition opening. Insertion is often performed with cranes and/or block and tackle gear to hold combustor weight, in conjunction with human alignment of the combustor basket with its receiving receptacle within the combustor case. The combustor length is much greater than radial clearance between the combustor basket outer circumference and other turbine components that are inside or outside the combustor case. A small yaw deviation of the combustor from the desired insertion path may result in inadvertent impact contact between the combustor and another turbine component—possibly resulting misalignment of combustor internal components (e.g., injectors, instruments, swirlers, nozzles, venturi, etc.) out of conformance with alignment and function specifications. In known turbine designs there is insufficient clearance between a fully assembled combustor and other turbine components that are external the combustor case, so it becomes impossible to align and insert a fully assembled combustor. Fully assembled combustor weight of over 1200 pounds (545 kg) further complicates precise combustor alignment during installation, especially if alignment is primarily performed by human operators.
Given lack of fully assembled combustor installation clearance and alignment complexities that are exacerbated by combustor weight, the known industry solution is to assemble combustor sub components in situ within the combustor case access port during initial assembly, service and field maintenance and insertion of the combustor. Assembly of sub components within a combustor access port to build a complete combustor and subsequent inspection for conformity with alignment/performance specifications is much slower than factory or authorized service facility bench assembly and inspection. Factory and/or service center pre-assembly in a controlled environment may also be performed by dedicated assembly specialists who may have more practical assembly experience and skills than some field personnel who must perform a broader range of repair services. Unfortunately pre assembly of drop in combustors is not feasible if there is insufficient installation clearance for fully assembled units, or if required installation precision alignment cannot be achieved reliably and consistently in the field due to component gross weight or lack of precise alignment fixtures.
There is a need for pre assembled industrial gas turbine combustors that are pre inspected and certified for meeting assembly and functional specifications that thereafter may be field installed as modular drop-in units.
There is another need for industrial gas turbines with sufficient external clearance outside the combustor case that facilitate direct alignment and installation of pre-assembled combustors into combustor case access ports along an installation path without undue risk of inadvertent combustor contact/impact with other turbine components inside or outside the combustor case, that may damage the combustor.
There is an additional need for a combustor handling tool and combustor installation method that facilitate alignment and insertion of heavy pre-assembled combustors, preferably under automatic control, with repeatable manipulation steps. Ideally such a combustor handling tool can remain permanently installed proximal the combustor case access ports for use as needed, or easily transported to and reassembled at various job sites by repair personnel.